Are you facing a lonely Valentine's Day? You'll never be alone again once Cymothoa exigua crawls into your mouth. This parasite will eat and replace your tongue:

When one of these crustaceans encounters a rose snapper, it enters the fish's mouth and steadily devours the fish's tongue. Once it has done this, the crustacean uses hooks on its underside to attach itself to the floor of the fish's mouth and thereafter serves as a replacement tongue (Figure 2.8).